The purpose of the proposed work is to determine if single chain intracellular antibodies, sFv intrabodies, directed against the HIV-l integrase protein can prevent the integration of HIV-1 in susceptible cells. In this project two anti-integrase monoclonal antibodies directed to different regions of the integrase protein will be engineered for cytoplasmic and nuclear expression in eukaryotic cells. The promoters will be optimized for efficient expression of the anti-integrase sFv intrabodies in several cell lines. Stable COS-i and CD4+ SupT cell lines expressing the sFv intrabodies will be established and challenged with different laboratory strains of HIV-1 to determine if the anti-integrase sFv intrabodies can inhibit integration of HIV-I DNA and production of infectious HIV-l virions. Also, the LN based moloney retrovira1 vector will be used to transduce the anti-integrase sFv intrabodies into uninfected cells which will be subsequently tested for inhibition of HIV-I integration and replication. ff these studies are successful, the anti-integraSe antibodies may be useful gene therapies for HIV-l infection.